Time-resolved nanosecond optical pyrometry of the vapor to plasma transitions in exploding bridgewires.

Electrically exploded wires find uses throughout high-energy physics. For example, they are commonly used as high-temperature sources, X-ray generators, and in precision timing detonators. However, the detailed and complete physics that occurs is complex and still poorly understood. A full mechanistic description of these complex phenomena is beyond the scope of a single paper. Instead, we focus on the formation of metal vapor and its transition to plasma. This single transition is commonly assumed to comprise "bridge-burst". We use a suite of diagnostics including a novel, fiber-based, high-speed, optical pyrometer to better characterize this transition. The primary finding from this project is that peak light output from an exploding wire does not temporally match the peak temperature. Additionally, it is found that peak light does not align with peak bridge-burst voltage and that the peak temperature is not voltage-dependent. These findings are non-intuitive and will allow for the correction of false assumptions previously made about this topic.

A review of the mechanism by which exploding bridge-wire detonators function.

An introduction to exploding bridge-wire (EBW) detonators is given followed by an extensive critical review of open source literature pertaining to these devices. The aim is to better establish the mechanism of operation. Some authors state that the key mechanism is shock-to-detonation while others maintain it is more thermal in nature, or a complex combination of both. In addition to EBW detonators, arc detonators and direct optical initiation detonators are also reviewed, and it is demonstrated that in this manner the usually coupled effects from both shock and deflagration can be somewhat decoupled. As a result, it is hypothesized that the mechanism of operation in all three detonators is in fact the same: the formation of a hot plasma with a power of ≈1 MW and emission in the ultraviolet drives a thermal explosion process.

The effect of tibial implant size on post-operative alignment following medial unicompartmental knee replacement.

We have retrospectively reviewed a consecutive series of 71 medial unicompartmental knee replacements in 56 patients performed between 1991 and 1996 by a single surgeon. The aim of this study was to quantify the amount of correction in the tibiofemoral angle, which is achievable with each thickness of polyethylene tibial insert. Our results have shown that the amount of correction which can be expected with an 8 mm, 10 mm, 12 mm and 14 mm insert are 5.3 degrees, 4.8 degrees, 6.6 degrees and 9.5 degrees, respectively. These results will act as a useful reference for surgeons who perform this procedure.

Construction of a high-resolution moiré interferometer for investigating microstructural displacement fields in materials.

A high-magnification moiré interferometer has been constructed with a spatial resolution of the order of 1 microm to measure the local in-plane displacement field associated with a material's microstructure. Laser illumination passes through phase-stepping optics and is delivered to the microscope head by polarization-preserving single-mode optical fibres. The head itself is a compact unit consisting of collimating optics, an objective lens and a charge coupled device (CCD) camera. Thin-phase gratings are cast onto the sample surface with a compliant epoxy resin and coated with ca. 5 nm of gold to enhance the fringe contrast and reduce speckle noise. By switching between the laser illumination and white-light illumination, the underlying microstructure is viewed in exact registration with the measured displacement fields. The application of the instrument is illustrated here by visualization of displacement fields in polymer-bonded explosives (PBXs) during deformation to failure. PBXs are highly filled polymers consisting of up to 95% by weight crystalline explosive bound in a variety of polymeric binders. The mechanical properties of PBXs are highly dependent on the microstructure, and moiré interferometry is an ideal tool for investigating the relationship between the 1-100 microm sized crystals and the displacement fields. Methods such as this are required if computer models of inhomogeneous materials are to be accurately validated.

The huckstep nail. Stable fixation of mechanically deficient femoral bone.

A Huckstep intramedullary nail was used to treat 23 fractures in which the femur was mechanically deficient due to pathologic fracture, nonunion, or complex fracture in osteoporotic bone. All nailings were performed by open surgery, and in some cases this was augmented by corticocancellous bone grafting. The Huckstep nail allows the use of multiple cross screws at 15-mm intervals, providing immediate and adequate stability with successful early postoperative weightbearing. The results at followup were good in functional and radiologic terms, with no cases of fixation failure or infection. The quality of instrumentation allowed the nail and screws to be inserted without difficulty; however, the straight profile of the nail may cause problems in the distal femur, as seen in 1 patient. The authors conclude that this device offers significant mechanical and practical advantages over most other forms of fixation, where early weightbearing is desired in the presence of deficient bone. It is not ideal for distal femoral fractures, particularly in the presence of excessive femoral bowing.

The natural history of meniscal tears in anterior cruciate ligament insufficiency.

We reviewed the meniscal status of 176 consecutive patients undergoing anterior cruciate ligament reconstruction acutely (less than 6 weeks from injury), subchronically (6 weeks to 12 months from injury), and chronically (more than 12 months from injury). The commonest tear was the single longitudinal vertical split of the medial meniscus. There was an increasing incidence of meniscal tears as the injury became more chronic, with a significant (P < 0.001) increase in medial meniscal tears; the incidence of lateral meniscal tears remained relatively constant. Seventy-five (43%) of the patients had one or both menisci repaired. Acutely, repair was performed more frequently on the medial meniscus than the lateral (80% versus 24%, respectively). All repaired menisci had single longitudinal tears unstable to probing. The incidence of repair dropped to 46% in the medial meniscus and 14% in the lateral meniscus in the chronic stage. Nineteen (25%) of these 75 patients (26 menisci) underwent a check arthroscopy at a minimum of 6 months from repair. All 21 medial menisci and all 5 lateral meniscal tears had healed; however, 1 lateral meniscus had torn along the line of the sutures. At an average followup of 40 months, 92% of the repaired menisci were still in situ and 8% that had required resection were related to the recurrence of anterior cruciate ligament instability. This study highlights the increasing incidence of meniscal injury in chronic anterior cruciate ligament insufficiency with the meniscal tears becoming more complex and therefore less amenable to suture.(ABSTRACT TRUNCATED AT 250 WORDS)

Simultaneous rupture of the ligamentum patellae, medial collateral, and anterior cruciate ligaments. A case report.

We report a case of simultaneous rupture of the ligamentum patellae, medial collateral, and anterior cruciate ligaments. The full extent of the injury was not recognized on clinical examination. Although this is a rare combination of injuries, the integrity of the extensor mechanism should always be confirmed in knee injuries.

Segmental fracture of the femoral stem of a low-friction arthroplasty. A case report.

Fracture of the femoral stem of a cemented hip arthroplasty is a well documented complication. However, double or segmental fracture is extremely rare, with only one other case appearing in the literature. The authors report a second case and discuss its etiology. They stress the importance of prolonged careful review of patients following total hip arthroplasty in order to obviate complications.

Patellar resurfacing in total condylar knee arthroplasty. Technique and results.

One hundred thirty-two total condylar knee arthroplasties with a 3-8-year follow-up period were studied prospectively with particular reference to the patellofemoral joint. All patients had significant patellofemoral disease and underwent primary patellar resurfacing. After operation 96% of patients had little or no pain and 98% had functional improvement. There were seven (5%) complications related to the patellofemoral joint. The importance of careful attention to preparation of the patella, the technique of prosthetic implantation and correct patellar tracking were emphasized. Routine patellar resurfacing proved highly successful with minimal complications.

Treatment of displaced subcapital fractures with the Charnley-Hastings hemiarthroplasty.

Between December 1982 and June 1986, 98 displaced subcapital femoral neck fractures were treated using the Charnley-Hastings bipolar hemiarthroplasty. Although the patients were elderly, often with associated medical problems, the operation was well tolerated and the mortality at one and six months was 14.4% and 24.5% respectively. Fifty-four hips were reviewed after an average follow-up of 33 months; 64.8% of patients had a good or excellent result. The fair or poor results were seen mainly in patients with poor pre-operative mobility and multiple medical problems. A significant cause of morbidity was dislocation (two interprosthetic) which occurred in six hips. There were two cases of deep sepsis but neither patient was fit for further surgery. There were no cases of acetabular erosion requiring revision surgery.

Luxatio erecta--two cases without direct injury.

Two cases of erect dislocation of the shoulder occurring during racket sports without associated falls or direct violence to the shoulder are reported. Both were mistaken for anterior dislocations and in one, with unrecognized brachial plexus injury, reduction was delayed with subsequent prolonged and incomplete neurological recovery. Erect dislocation should be recognized as a separate entity with a high incidence of neurological damage and requiring a different method of reduction.